• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.383-390
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• 2006

In this paper, a stochastic field that is compatible with Monte Carlo simulation is suggested for an expansion-based stochastic analysis scheme of weighted integral method. Through investigation on the way of affection of stochastic field function on the displacement vector in the series expansion scheme, it is noticed that the stochastic field adopted in the weighted integral method is not compatible with that appears in the Monte Carlo simulation. As generally recognized in the field of stochastic mechanics, the response variability is not a linear function of the coefficient of variation of stochastic field but a nonlinear function with increasing variability as the intensity of uncertainty is increased. Employing the stochastic field suggested in this study, the response variability evaluated by means of the weighted integral scheme is reproduced with high precision even for uncertain fields with moderately large coefficient of variation. Besides, despite the fact that only the first-order expansion is employed, an outstanding agreement between the results of expansion-based weighted integral method and Monte Carlo simulation is achieved.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.889-891
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• 2004

본 논문은 약 134 GB에 이르는 시간 가변 해양 볼륨 데이터론 효과적으로 가시화 하기 위한 두 가지 접근 방법을 제시한다. 첫 번째 방법은 고화질의 동영상을 생성하기 위한 오프라인 병렬 볼륨 렌더링 기법으로, 볼륨광선추적법과 등가면 기법을 통합한 렌더링 알고리즘을 적용하여 고해상도의 영상을 생성할 수 있다. 두 번째 방법은, 그래픽스 하드웨어 가속기능을 통해 대화식 가시화가 가능한 멀티 파이프 렌더링을 구현하는 것으로, 복수개의 그래픽스 파이프라인과 3차원 텍스춰 맵핑 가속기능을 이용해 시간의 변화에 따른 해양의 변화를 효과적으로 가시화하고 분석할 수 있다.

• Electrical & Electronic Materials
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• v.2 no.2
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• pp.143-151
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• 1989

본 논문은 압전 세라믹스 재료를 사용한 장방형 압전 변압기의 승압특성에 관한 연구이다. 승압기구 분석을 위하여 진동모드에 따른 주파수 Spectrum을 구동부측곽 발전부측에 대해 각각 조사하였다. 시편구조(전극길이, 두께, 폭)에 따른 진동상태와 승압비를 평가하고 압전 변압기로써 가져야 될 최적조건을 제시하였다. 또한 부하저항에 병렬로 연결된 등가손실저항과 발전부 공진임피던스 사이의 관련성을 검토하였다.

• The Journal of the Acoustical Society of Korea
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• v.12 no.1E
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• pp.48-55
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• 1993

초음파 탐촉자의 개발에 필요한 압전재료의 선택을 위하여 탐촉자의 성능에 영향을 미치는 탄성, 유전, 압전 상수의 영향을 알아보았다. 해석 방법으로는 등가회로를 통한 두께 모드 발신기, 수신기, 펄스 반사기의 전달함수를 구하였으며, 이로부터 압전재료의 각 물성치가 가져야 할 바람직한 특성을 제시하였다. 본 연구의 결과는 재료의 선택시와 더불어 세라믹 공학자들이 초음파용 압전소자를 개발함에 있어 적절한 지침이 될 수 있을 것이다.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.82-87
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• 2014

MLI(Multi-layer Insulation) is widely used to get highly insulating on cryogenic system in order to reduce heat loads. MLI for satellites thermal performance is changed by materials and laminated method. In this study, a composite multilayer insulation by application of heat stroage tank performance were compared with materials and laminated to change the way. Experimental methods of the KS C 9805 was used, the composite multilayer insulation and EPS was compared with the insulation performance. A method for analysis of experimental results is the equivalent thickness about CMI and the insulation performance were used to compare thermal conductance. As a results, the equivalnet thickenss and the thermal conductance of the composite multilayer insulation were smaller than the EPS and the thermal performance are more excellent. In addition, the configuration of the composite multilayer insulation materials and laminated method varies depending on the overall heat transfer coefficient was confirmed.

• Economic and Environmental Geology
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• v.50 no.1
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• pp.61-71
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• 2017

The effects of joint density and size distribution on the hydrogeologic characteristics of jointed rock masses are addressed through numerical experiments based on the 2-D DFN (discrete fracture network) fluid flow analysis. Using two joint sets, a total of 51 2-D joint network system were generated with various joint density and size distribution. Twelve fluid flow directions were chosen every $30^{\circ}$ starting at $0^{\circ}$, and total of 612 $20m{\times}20m$ DFN blocks were prepared to calculate the directional block conductivity. Also, the theoretical block conductivity, principal conductivity tensor and average block conductivity for each generated joint network system were determined. The directional block conductivity and chance for the equivalent continuum behavior of the 2-D DFN system were found to increase with the increase of joint density or size distribution. However, the anisotropy of block hydraulic conductivity increases with the increase of density discrepancy between the joint sets, and the chance for the equivalent continuum behavior were found to decrease. The smaller the intersection angle of the two joint sets, the more the equivalent continuum behavior were affected by the change of joint density and size distribution. Even though the intersection angle is small enough that it is difficult to have equivalent continuum behavior, the chance for anisotropic equivalent continuum behavior increases as joint density or size distribution increases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.311-316
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• 2015

This paper presents a design method for thin but wideband absorbers using resistive sheets. Its equivalent circuit consists of a series RLC resonant circuit and a short-terminated transmission line. Based on this equivalent circuit, we presented the three conditions for an electromagnetic absorber which has a thickness less than a quarter wavelength and wide absorption bandwidth at center frequency. By using an root-finding algorithm, the equivalent resistance, capacitance, and inductance of the absorbers are obtained. These equivalent circuit values for the absorber surface can be realized by a 2D periodic cross-shaped structure which has required surface resistance. Using the design method, we have designed the absorber which has 18.75 mm($67.5^{\circ}$ electrical length) thickness and 90 % absorption bandwidth of 116 % bandwidth at 3 GHz.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.189-197
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• 2012

The cold-formed steel stud, which has been used as a load-bearing member of wall panels for steel houses, poses a significant problem in insulation due to heat bridging of the web. Therefore, some additional thermal insulating materials are required. In order to solve this problem, the cold-formed steel thermal stud with slits in the web was developed. However, estimating the structural strength of thermal studs is very difficult because of the arrangement of perforations. In this paper, an analytical and experimental research on thermal studs is described. Three types of studs with different length, pitch and arrangement of slits were tested to failure. A simple design approach was proposed based on the test results. The proposed method adopted the direct strength method, based on the elastic local and distortional buckling stress of plain studs with equivalent thickness in the web instead of thermal studs. The predictions using the proposed method were compared with test results for verification and the adequacy of the proposed method was confirmed.

• Journal of The Korean Association For Science Education
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• v.24 no.3
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• pp.612-620
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• 2004

The purpose of this study was to investigate how middle and high school students represent circuit diagrams with different shapes but electrically same. What prototypes of circuit which students possessed were, how students represented the connection of resistors, and what criteria used while grouping the circuit diagrams were investigated. The participants were 10 middle and 10 high school students. The results show that they represented the circuit diagrams by the geometrical resistor configurations rather than physics principles, not considering the presence of a junction or a battery on the branch. This representation was constrained by the circuit prototypes. Middle and High school students seems to have the own way of representing circuit diagrams without considering physics principles.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.47-54
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• 2016

In this study, the flexural capacity of fiber reinforced concrete floor slabs were evaluated using main design loads, racking and moving loads. Based on design standards and guidelines, the magnitude and loaded area of each load were determined, and its relationship was assessed. For the application of a single load, flexural capacity should be evaluated in the edge of a floor slab. In addition, the slab with thickness and concrete strength, greater than 180mm and 35MPa, respectively, sufficiently satisfied flexural capacity with a minimum of equivalent flexural strength ratio. The combination of racking loads required the largest equivalent flexural strength ratio to satisfy the flexural capacity of the floor slab. The combination of racking and moving loads showed equivalent flexural strength ratio smaller than the case of combination of racking loads, but larger than the application of single racking or moving loads. The results of this study indicated that the flexure of fiber reinforced concrete floor slabs should be designed using the combination of design loads.